The German Offenlegungsscnrift 36 11 063 discloses a saw blade with teeth in a recurring cycle. Each cycle also comprises a group of teeth, so that the number of teeth in a group is equal to the number of teeth in a cycle. The teeth in one group with respect to the cycle of teeth are differentiated as being either a leading tooth, this being one or more of the first teeth of a group or cycle, or as being following teeth. The leading tooth or teeth are often formed as unset teeth, whereas the following teeth in most cases are formed to be set teeth. Usually all teeth are of the same width. The leading tooth has the greatest height, and the height decreases in a group. Sometimes the leading tooth is phased or its cutting edge is broken by a chip breaking flute . The following teeth are usually formed as teeth set alternately to the left and right to create a cutting channel wider than the basic body of the saw blade. When two leading teeth are provided, these can be stepped like the well known roughing and finishing teeth of a circular saw blade, by which the effective edge is distributed between the two leading teeth. The cycle is completed by the set following teeth, which create a wider cutting channel. The decrease of height usually occurs in a step-like fashion, but there are embodiments with teeth which are different with regard to their height and are arranged in the cycle in a non regular way. In one of the depicted embodiments seven teeth are provided, with an unset leading tooth, which has a straight cutting edge the width of the basic body. Following this leading tooth are three pairs of following teeth, all of which are set alternately to the left and right.
The last two pairs of following teeth may have identical set width in conjunction with equal or unequal height of the teeth, so that these last four following teeth define the width of the cutting channel and work alternately on the two facing surface planes of the cutting channel. For instance, the fifth and seventh teeth in a group comprised of seven teeth will work on the same surface of the cutting channel. The seventh tooth performes a following work step in relation to the fifth tooth, which serves to compensate the deviation from the path caused by the fifth tooth.
In a further embodiment five teeth are provided in a group and therefore in a cycle. The first tooth is unset, whereas the four following teeth are set teeth. The setting of the first and fourth following teeth is greater than that of the second and third following teeth, though. Therefore each surface of the cutting channel is worked on by a single tooth of the group only. This is also the case when two set leading teeth are used in place of one unset leading tooth.
The German Offenlegungsschrift 36 11 063 also describes an illustrative embodiment which employs no set teeth but only unset teeth in a group of teeth with respect to a cycle of teeth. In one group two following teeth are assigned to one leading tooth. The height of the teeth in a group decreases and the width increases. The last, widest tooth is provided once only. All the teeth are formed symmetrically with respect to a longitudinal center plane through the basic body. The present invention uses such a saw blade as a starting point. The first tooth in a group of teeth has a straight and continuous cutting edge perpendicular to the longitudinal center plane of the saw blade. The width of this first tooth is equal to the width of the basic body. Both of the two following teeth also have cutting edges perpendicular to the longitudinal center plane of the basic body, of which, due to the increasing width, only the outer parts contribute to the cutting process. The following teeth have differing flank angles and the angle enclosed between flank and cutting edge is also different for each of the following teeth, but in each case it is an acute angle. The effective cutting edge decreases in length from tooth to tooth, so that the main contribution to the cutting process is provided by the leading tooth and the two following teeth only widen the cutting channel, so that a clearance cut is achieved. This embodiment of a saw blade is intended to coincide in function and effect with the embodiments in which set teeth are used. While set teeth can be manufactured without too much difficulty, a saw blade with unset teeth of different width is extremely elaborate in production, it not being clear how the greater width of the following teeth as compared to the width of the basic body is to be achieved in the first place. In addition, this embodiment with unset teeth displays numerous other disadvantages. The effective part of the cutting edge of the following teeth and their flank enclose an acute angle, i.e. an angle of less than 90.degree., so that these lateral tips of the teeth are subjected to substantial wear during the cutting process, by which the width of the cutting channel rapidly decreases. With set teeth this disadvantage does not occur to such a great extent, because the angle between effective cutting edge and flank is always about 90.degree.. Set following teeth are always unfavorable for the straight running of a saw blade, though, because lateral forces are created by them. These forces, acting on one side only, cause a deflection of the set tooth concerned. This not only results in a poorer surface quality of the cut face in the cutting channel, but also causes vibrations of the saw blade. The unset leading tooth has no lateral clearance so that its flanks cause friction in the cutting channel. The leading tooth must perform the main cutting work and clear the greatest cross section. The same holds for more than one leading tooth in a group of teeth; in all cases the set teeth are loaded less. All embodiments of the known saw blade attempt to achieve that both leading and following teeth contribute to the cutting process. The chips are reduced to a small size, which makes their removal easier and enables a higher cutting speed. By including buffer teeth, the load on the leading teeth is reduced and distributed more evenly among all teeth. From the German Offenlegungsschrift 25 16 137 a circular saw blade is known, in which a cycle comprises a group of teeth having a pre cutter and a final cutter. The pre-cutter and final cutter teeth have the same tooth-height and their width is the same as that of the basic body. The pre-cutter and final cutter teeth have differently angled phases, so that different chips are removed by the respective cutters in the known way. The achievable surface quality is comparably poor, due to the fact that there is friction between the basic body and the adjacent material in the cutting channel.